Application of silicon substrates for high-T_c Josephson junctions and SQUIDs

Abstract
We investigated the realization of YBCO Josephson junctions and SQUIDs on 10x10 mm² silicon bicrystal substrates and on 2 inch single crystalline silicon wafers. All buffer layers, YBCO films, passivation and metallization layers were deposited with the laser ablation technique. Bicrystal junctions with RSJ-like I-V characteristics, I_CR_N products of 150 µV at 77 K and microwave response up to the THz range were realized. DC-SQUIDs consisting of these junctions have working temperatures up to 80 K and transfer functions up to 30 µV/Φ₀; at 77 K. Further we enlarge our standard preparation technique of Josephson step-edge junctions on 5x10 mm² to 2 inch silicon wafers. YBCO films of this size have a critical temperature T_c > 87 K and critical current densities j_c (77K) > 3-10⁶ A/cm² over the whole wafer area.